Until you've successfully entered your registration code into PixelToy, it will continue to stamp "pixeltoy" in the corner of exported QuickTime movies.

While running PixelToy, select "Register..." from the PixelToy menu and enter your user name and registration code, exactly as given in your registration e-mail. It may be helpful to copy/paste them instead of typing them, as they do have to be exactly the same.